Blac Chyna Says Woman in New Sex Tape Sure Looks Like Her, But It's Not

Blac Chyna says a new sex tape floating around featuring a woman who's the spitting image of her is just that ... a spitting image, but it ain't her.

An out of focus, 13-minute video surfaced online just after Chyna's oral sex vid with Mechie leaked.

The new video shows a woman with Chyna's skin tone, body type and hairstyle engaging in sexual intercourse with an African-American man. The woman has several tattoos on her body, just like Chyna.

The video first popped up on Twitter, but has since spread to popular porn sites trying to pass it off as her.

Sources close to Chyna admit ... the woman in the grainy footage does have significant similarities to the reality star, but it is absolutely NOT her.

We're told Chyna's legal team has fired off more than 20 cease and desist letters to the porn sites that are hawking the video using Chyna's name. Her lawyers have also sent the letters to porn sites showing her oral sex tape with Mechie.